Remifentanil for awake intubation

Awake fibreopic intubation (AFOI) is indicated in a subgroup of critically ill patients in whom RSI is contraindicated due to a predicted difficult airway, and in whom time pressures do not mandate a more immediate route to the airway. Last night I intubated a patient with a swollen tongue using this technique, under remifentanil sedation. It was interesting to subsequently see that this month’s Anaesthesia contains an article on ‘remi’ for AFOI:

Remifentanil is increasingly being used as the primary agent to provide sedation during awake fibreoptic nasal intubation. In this observational study, we aimed to determine the optimal effect site concentration of remifentanil, using a target controlled infusion based on the Minto pharmacological model, to provide optimal safe intubation conditions without the use of other sedatives/premedication and/or spray-as-you-go local anaesthesia. Twenty patients with anticipated difficult airway participated in the study. Good intubating conditions were achieved in all patients with mean (SD) effect site concentration of 6.3 (3.87) ng.ml(-1) of remifentanil recorded at nasal endoscopy and 8.06 (3.52) ng.ml(-1) during tracheal intubation. No serious adverse event occurred during any of these procedures. These preliminary findings suggest that this is a feasible and safe technique for awake fibreoptic nasal intubation.

Those of us not familiar with target controlled infusions might find a dose in micrograms per kilo more helpful. This paper from Analgesia and Anesthesia provides a useful guide, comparing relatively high and low doses of loading and maintenance doses:

Awake nasotracheal fiberoptic intubation requires an anesthetic management that provides sufficient patient comfort, adequate intubating conditions, and stable hemodynamics. Short-acting and easily titratable analgesics are excellent choices for this maneuver. In this study, our aim was to determine an appropriate dosage regimen of remifentanil for awake nasotracheal fiberoptic intubation. For that reason, we compared two different dosage regimens. Twenty-four patients were randomly assigned to receive remifentanil 0.75 micro g/kg in bolus, followed by a continuous infusion of 0.075 micro g x kg(-1) x min(-1) (Group L), or remifentanil 1.5 micro g/kg in bolus, followed by a continuous infusion of 0.15 micro g x kg(-1) x min(-1) (Group H). All patients were premedicated with midazolam 0.05 mg/kg IV and glycopyrrolate 0.2 mg IV. Both dosage regimens ensured patient comfort and sedation. Discomfort did not differ between groups. Patients in Group H were sedated more profoundly. Hemodynamic stability was maintained with both remifentanil doses. Intubating conditions were adequate in all patients and comparable between the groups. The large dosage regimen did not result in any additional benefit compared with the small dosage. For awake nasotracheal fiberoptic intubation, we therefore recommend remifentanil 0.75 micro g/kg in bolus followed by continuous infusion of 0.075 micro g x kg(-1) x min(-1), supplemented with midazolam 0.05 mg/kg

An alternative to bolus + maintenance is using an incremental infusion rate via an infusion pump. In a comparision with midazolam and fentanyl, remifentanil was given to 37 patients in incremental dosages (0.1-0.25-0.5 microg/kg/min) by an infusion pump according to comfort, level of sedation and respiratory depression. Nasotracheal intubation was better tolerated in the remifentanil group, who also showed better suppression of haemodynamic effects of intubation.

BACKGROUND: Awake fiberoptic intubation is the standard of care for difficult airway management. Quality and success of this technique depend on the experience of the intubating physician and the proper preparation of the patient. The aim of this study was to compare remifentanil (R) as single agent to the combination of fentanyl (F) and midazolam (M), which have been the drugs for analgesia and sedation for this procedure.

METHODS: Seventy-four adult patients requiring nasotracheal intubation were randomly assigned to one of two groups. In group I, (n=37) R was administered in incremental dosages (0.1-0.25-0.5 microg/kg/min) by an infusion pump according to comfort, level of sedation and respiratory depression. In group II, (n=37) analgesia and sedation was achieved by F 1.5 microg/kg and doses of between 1 and 10 mg M, titrated to the individual needs. Patient reactions like grimacing, movement and coughing during intubation were assessed, as well as patient recall of the procedure. Haemodynamic and respiratory parameters were continuously recorded.

RESULTS: Group I patients better tolerated nasal tube passage (P<0.001) and laryngeal tube advancement (P<0.001) than group II. Remifentanil better suppressed hemodynamic response to nasal intubation (P<0.001). No significant difference in respiratory data was recorded. In group I more recall of the procedure was observed (six vs. zero patients, P<0.05).

CONCLUSION: Remifentanil in high doses, as the single agent for patient preparation for awake fiberoptic intubation seems to improve intubating conditions, quality and reliability of the procedure. However, a higher incidence of recall is to be expected.

Some authors advocate dexmedetomidine for AFOI. Remifentanil was compared with dexmedetomidine in a randomised, double-blind trial. Remi was loaded and maintained at the ‘low’ dose as described in the second paper above and was associated with a higher intubation success rate on first attempt than dexmedetomidine (76% vs 38%):

Introduction: Dexmedetomidine (DEX), a centrally acting, selective alpha-2 agonist, with analgesic and sedation properties, has been successfully used for sedation in intensive care units. Remifentanil (REM), an ultra-short acting synthetic opioid, is often used to aid awake fiberoptic intubation (AFOI). As a narcotic, REM has a potential for respiratory depression, whereas DEX does not. This study compares the use of REM and DEX as adjuncts to local anesthetic preparation of the airway for AFOI.

Methods: Thirty adult ASA I-III patients with expected difficult airways were randomized to receive REM or DEX for sedation during AFOI. Operators and assessors were blinded to the drug used. Preoperatively, all patients received 2 mg midazolam intravenously and their airways were topicalized with 4% lidocaine. Patients in the REM group received a bolus of 0.75 mcg/kg over 10 minutes followed by an infusion of 0.075 mcg/kg/min. Patients in the DEX group received a bolus of 0.4 mcg/kg over 10 minutes followed by an infusion of 0.7 mcg/kg/hr. A word and picture set was presented to each patient before any drugs were administered, after loading of either sedative, and following extubation. Heart rate, blood pressure, respiratory rate, SpO2, bispectral (BIS) index level, and Ramsay sedation level (RSS) were recorded. Recall of each 3 sets of pictures and words was assessed at 30 minute intervals for a period of 3 hours after the completion of surgery.

Results: Patient demographics were similar between the 2 groups. All patients’ airways were successfully secured by fiberoptic intubation. Seventy-six percent of REM cases were intubated on the first attempt, as compared to 38% of the DEX cases (p=0.02). Intubation attempts were greater in the DEX group even after adjusting for confounders (OR unadjusted = 5.26, 95% C.I. = 1.19, 25.72; OR adjusted = 4.84, 3.43, 6.82). The DEX group had a higher mean oxygen saturation rate than REM (1.58 higher; 95% C.I. = 0.14, 3.03; p=0.03). Although the incidence of O2 saturation < 90% was greater in the REM group, it was not significant. No apneic episodes occurred and no rescue maneuvers, such as administration of reversal drugs or positive pressure ventilation, were required in either group. There was a lower Ramsey Sedation Scale (RSS) score (lower by = 0.45, 95% C.I. = 0.1142, 0.7792; p=0.008) in the DEX group compared to the REM group. A Kaplan Meier survival analysis showed that DEX patients took longer to attain a RSS of 3 despite reaching a lower RSS score. (Logrank test = 4.00 with one degree of freedom, p=0.0455) The DEX group also had 6.99 lower (95% C.I. = 1.19, 12.79; p=0.018) BIS score compared to the REM group. Generalized estimating equations (xtgee) showed no significance in the recall results with the exception of verbal recall in the DEX group after the initial bolus. Minimal hemodynamic instability was observed in both groups.

Discussion: Both Dex and REM can be safely used as sedative agents for AFOI. Despite increased sedation and lower recall after the initial bolus, the DEX group required more attempts at intubation. Nonetheless, lower oxygen saturation was observed in the REM group.